Refrigerant circuit

ABSTRACT

The invention includes a refrigerant circuit for a cooling operation and a heat pump operation. The refrigerant circuit has a high pressure area and a low pressure area, including at least one heat source/heat sink, a compressor, an expansion device, at least one thermal interior space module, and an internal heat exchanger. The internal heat exchanger has a high pressure side part and a low pressure side part, wherein the high pressure side part is disposed between the expansion device and the heat source/heat sink. The invention also includes at least one metering device through which the high pressure side part of the internal heat exchanger is operable during the heat pump operation at a medium pressure level intermediate a pressure level in the high pressure area and a pressure level in the low pressure area of the refrigerant circuit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of German Patent Application No. DE10 2011 109 506.7 filed Aug. 5, 2011, the entire disclosure of which ishereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention involves a refrigerant circuit for a vehicle, and moreparticularly a refrigerant circuit for a vehicle configured to optimizeperformance of an internal heat exchanger during a cooling operation anda heat pump operation.

BACKGROUND OF THE INVENTION

DE 103 09 779 A1 discloses a double-loop air conditioner in whichrefrigerant is heated in a heat pump or through a compression of therefrigerant, and is then released to a condenser in an interior spacemodule (hereinafter referred to as the heat register) for heating aninflow of air into an interior space. In addition, heat can be takenfrom a refrigerant circuit of a motor and directed to the refrigerantthrough a heat transfer device, or an inflow of air into the interiorspace may be heated in a conventional heating device via a heating corethrough which the refrigerant flows. In a cooling device, heat isremoved from the inflow of air into the interior by a condenser, whichin this operation works as an evaporator. The heat given off to acooling material is thereupon released to the environment throughanother condenser.

DE 101 58 104 B4 discloses an air conditioner that has a refrigerantcircuit in which heat in a heat pump process is taken from an outsideair. The heat is released for heating an interior space inflow of airunder high pressure through a condenser, which functions in a heatingunit as a gas cooler or as a condenser.

It is known that a refrigerant circuit that is appropriate for bothcooling and heat pump operation has a high and low pressure area. Such arefrigerant circuit includes at least one heat source or heat sink, suchas a gas cooler or condenser and/or a glycol heat exchanger, as well asa compressor, an expansion module, at least a thermal interior spacemodule and a refrigerant storage area.

In addition, an internal heat exchanger is provided, which has a highpressure side part and a low pressure side part, whereby the highpressure side part of the internal heat exchanger in the heat pump liesbetween the expansion module and the gas cooler. The low pressure sideof the internal heat exchanger is arranged on a suction side of thecompressor.

A disadvantage of the refrigerant circuit is that no heat exchange withthe low pressure side part of the internal heat exchanger in the heatpump operation can occur without significant technical effort since theinternal heat exchanger in the heat pump is disposed in the low pressurearea of the refrigerant circuit. The internal heat exchanger isrelatively inactive in the heat pump operation.

Further, the heat pump contains an excessive amount of the refrigerantsince a filling amount is determined according to the air conditioneroperation. As a result, suctioning of the refrigerant into thecompressor is unavoidable, thereby decreasing an efficiency of thecompressor.

Accordingly, it would be desirable to produce a refrigerant circuit fora vehicle configured to optimize performance of an internal heatexchanger during a cooling operation and a heat pump operation.

SUMMARY OF THE INVENTION

In concordance and agreement with the present invention, a refrigerantcircuit for a vehicle configured to optimize performance of an internalheat exchanger during a cooling operation and a heat pump operation, hassurprisingly been discovered.

In one embodiment, a refrigerant circuit for a vehicle, comprises: acompressor configured to compress a refrigerant; an internal heatexchanger in fluid communication with the compressor to receive therefrigerant therein, the internal heat exchanger including a highpressure side part and a low pressure side part, wherein the highpressure side part is in fluid communication with at least oneadditional heat exchanger; and at least one metering device configuredto control a pressure level of the refrigerant, the at least onemetering device in fluid communication with the internal heat exchanger,wherein the at least one metering device permits the high pressure sidepart of the internal heat exchanger to receive the refrigerant during aheat pump operation of the refrigerant circuit between a pressure levelat which the refrigerant exits the compressor and a pressure level atwhich the refrigerant enters the compressor.

In another embodiment, the refrigerant circuit for a vehicle, comprises;a compressor configured to compress a refrigerant; an internal heatexchanger in fluid communication with the compressor to receive therefrigerant therein, the internal heat exchanger including a highpressure side part and a low pressure side part, wherein the highpressure side part is in fluid communication with a condenser/gas coolerand a heat exchanger/chiller; and at least one controllable expansiondevice configured to control a pressure level of the refrigerant, the atleast one controllable expansion device in fluid communication with theinternal heat exchanger, wherein the at least one controllable expansiondevice permits the high pressure side part of the internal heatexchanger to receive the refrigerant during a heat pump operation of therefrigerant circuit between a pressure level at which the refrigerantexits the compressor and a pressure level at which the refrigerantenters the compressor.

In yet another embodiment, the refrigerant circuit for a vehicle,comprising: a compressor configured to compress a refrigerant; aninternal heat exchanger in fluid communication with the compressor toreceive the refrigerant therein, the internal heat exchanger including ahigh pressure side part and a low pressure side part, wherein the highpressure side part is in fluid communication with a condenser/gas coolerand a heat exchanger/chiller; a first controllable expansion deviceconfigured to decrease a pressure level of the refrigerant, the firstcontrollable expansion device in fluid communication with the internalheat exchanger and the condenser/gas cooler, wherein the firstcontrollable expansion device permits the high pressure side part of theinternal heat exchanger to receive the refrigerant during a heat pumpoperation of the refrigerant circuit between a pressure level at whichthe refrigerant exits the compressor and a pressure level at which therefrigerant enters the compressor; and a second controllable expansiondevice configured to decrease a pressure level of the refrigerant, thesecond controllable expansion device in fluid communication with theinternal heat exchanger and the heat exchanger/chiller, wherein thesecond controllable expansion device permits the high pressure side partof the internal heat exchanger to receive the refrigerant during theheat pump operation of the refrigerant circuit between the pressurelevel at which the refrigerant exits the compressor and the pressurelevel at which the refrigerant enters the compressor.

It is an objective of the invention to simplify a refrigerant circuit toassure an active operation of an internal heat exchanger during a heatpump operation. A further objective is to correspondingly storeunnecessary refrigerant in various operating conditions of the coolingand heating operation, and thus to optimally adjust a level ofcirculating refrigerant.

In certain embodiments, active operation of the internal heat exchangeris assured by relieving a stress of the refrigerant after the internalheat exchanger. A refrigerant storage area downstream from the internalheat exchanger in a heat pump is also supplied with standing refrigerantunder high pressure. However, the storage area is too large based on adensity of the refrigerant. Therefore, a sufficient buildup of pressureon the high pressure side may not be obtained.

According to the invention, the refrigerant circuit includes a meteringdevice through which the high pressure side part of the internal heatexchanger in the heat pump is driven to a medium pressure level, whichlies between the high and low pressure level of the refrigerant circuit.

A loss of pressure of the high pressure side of the inner heat exchangerto the heat source causes a pressure level of the stress-relievedtwo-phase refrigerant to be above that of the downstream heat source. Inextreme cases, an area of the medium pressure level can be increased ordecreased to correspond to the high pressure or low pressure level.

Because of the high specific heat of the two-phase refrigerant and theconstant temperature, the internal heat exchanger can be used activelyto superheat the refrigerant in the heat pump that flows through the lowpressure side part of the internal heat exchanger. Accordingly,operation of the compressor is assured, and a suctioning of therefrigerant into the compressor is avoided.

The configuration and function of the refrigerant circuit can beemployed regardless of the refrigerant used. At times, differences occurin particular pressure circumstances for low pressure, medium pressure,and high pressure levels.

In addition, wiring can be implemented independent of a drive design ofthe particular vehicle, be it conventional, hybrid, electric, etc., andthus independent of a type of the compressor.

In an advantageous embodiment, a metering device configured to drive thehigh pressure part of the internal heat exchanger to the medium pressurelevel is a damper. The damper is disposed downstream of the highpressure side of the internal heat exchanger during the heat pumpoperation, preferably downstream of a refrigerant storage area.

The damper is configured to produce a loss of pressure only in adirection of the flow of the refrigerant in the heat pump, dependent ona narrowing of a cross-section of the damper. In the air conditioner,the cross-section is maximized in an opposite direction of the flow ofthe refrigerant. A medium pressure level is adjusted by an expansionvalve in the heat pump. The expansion valve is relieved to low pressureby a decrease of pressure created by the damper after the refrigerantflows through the internal heat exchanger.

Preferentially, the metering device for achieving the medium pressurelevel is configured as a conduit adjustment of a conduit disposedbetween the heat source or heat sink and the expansion valve. Therefrigerant storage area and high pressure side part of the internalheat exchanger are also disposed between the heat source or heat sinkand the expansion valve.

A cross-section of the conduit and a conduit guidance or bends in theconduit can be calculated for each vehicle, so that no noticeable lossof pressure occurs during the cooling operation, while a defined loss ofpressure during the heat pump operation can be obtained for the heatingoperation.

In particular, the cross-section of the conduit is smaller than priorart. Accordingly, material for the conduits, and thus a cost and aweight can be minimized. A minimized conduit cross-section also resultsin a reduction in the amount for filling and a reduced need forrefrigerant over the prior art.

According to the invention, in addition to the controllable expansiondevice, which is disposed in the flow direction in the heat pumpupstream of the high pressure side part of the internal heat exchanger,at least one additional controllable expansion device can be employed.The additional controllable expansion device is disposed in the flowdirection downstream of the high pressure side part of the heatexchanger and downstream of the refrigerant storage area, yet upstreamof the heat source. The additional controllable expansion device, whichinitially is at a medium pressure level, can be decreased to a lowpressure level.

In another advantageous embodiment, in addition to a condenser as a heatsource or heat sink in the refrigerant circuit, an additional heatexchanger, in particular an external heat exchanger, can be provided asan additional heat source or heat sink for transferring heat between themotor and the refrigerant circuit. The additional external heatexchanger can be configured as a water-glycol heat exchanger (i.e. achiller). The additional heat exchanger can be located in therefrigerant circuit either parallel or serial to the condenser. In bothconfigurations, the conduit to the condenser and the conduit to theadditional heat exchanger branch from the conduit originating from thehigh pressure side part of the internal heat exchanger. In anadvantageous embodiment, the two branches can be combined together viaone controllable expansion device. The refrigerant stream flow to one ofthe branches can be determined by control of the expansion device bywhich switch valves are replaced. Additionally, the controllableadjustment of the medium pressure level in the internal heat exchangerand the refrigerant storage area is assured for both of the branches.

By disposing the controllable expansion device in the heat pumpdownstream of the refrigerant storage area, the pressure level in therefrigerant storage area—and according to the wiring variant in theinternal heat exchanger as well—can be flexible in a manner thatoptimizes the amount of refrigerant available in the refrigerantcircuit.

Furthermore, the invention involves a method for operating an airconditioner including a refrigerant circuit as described hereinabove,whereby at least one additional controllable expansion device isemployed in addition to the controllable expansion device disposed inthe flow direction in the heat pump upstream of the high pressure sidepart of the internal heat exchanger. The additional controllableexpansion device is disposed in the flow direction downstream of thehigh pressure side part of the heat exchanger and downstream therefrigerant storage area, yet upstream of the heat source.

According to the invention, the expansion devices are controlled anddefined during operation. In particular, in the heat pump, the expansiondevices are controlled to work individually, in which particularexpansion devices work individually, and any other expansion devices areopened fully. In another application, all the expansion devices can beoperated in combination with each other. In such case, the expansiondevices are opened in interaction with one another in order to obtain adesired pressure level. Preferentially, the expansion devices can beoperated alternately, as needed in combination, or individually.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other objects and advantages of the invention,will become readily apparent to those skilled in the art from readingthe following detailed description of a preferred embodiment of theinvention when considered in the light of the accompanying drawings inwhich:

FIG. 1 is a schematic flow diagram of a refrigerant circuit according toan embodiment of the invention, showing a cooling operation thereof;

FIG. 1A is a schematic flow diagram of the refrigerant circuitillustrated in FIG. 1, showing a heat pump operation thereof;

FIG. 2 is a schematic flow diagram of a refrigerant circuit according toanother embodiment of the invention, wherein the refrigerant circuitincludes a conduit having an adjustable cross-section;

FIG. 3 is a schematic flow diagram of a refrigerant circuit according toanother embodiment of the invention, wherein the refrigerant circuitincludes controllable expansion devices and serial connection of aplurality of heat exchangers; and

FIG. 4 is a schematic flow diagram of a refrigerant circuit according toanother embodiment of the invention, wherein the refrigerant circuitincludes controllable expansion devices and parallel connection of aplurality of heat exchangers.

DETAILED DESCRIPTION of EXEMPLARY EMBODIMENTS OF THE INVENTION

The following detailed description and appended drawings describe andillustrate various exemplary embodiments of the invention. Thedescription and drawings serve to enable one skilled in the art to makeand use the invention, and are not intended to limit the scope of theinvention in any manner. Equivalent components or components withequivalent effect are shown in the following examples of embodimentswith the same reference list number.

FIGS. 1 and IA show a schematic presentation of a refrigerant circuit 10of a vehicle air conditioner according to the present invention. Therefrigerant circuit 10 is suitable for both a cooling operation,illustrated in FIG. 1, and a heat pump operation, illustrated in FIG.1A. During the cooling operation shown in FIG. 1, a refrigerant underhigh pressure flows out of a compressor 12 through a valve 14, through acondenser/gas cooler 26, and through a metering device 22. As anon-limiting example, the valve 14 is a 3-2 way valve and the meteringdevice 22 is a damper. However, it would be understood to employ twoseparate controllable shutoff valves.

The metering device 22 is configured to decrease pressure only duringthe heat pump operation. On the other hand, during the coolingoperation, the metering device 22 produces no or minimal pressure loss.The refrigerant flows through a refrigerant storage area 24 and a highpressure side part of an internal heat exchanger 20 at a high pressurelevel HD. The pressure level of the refrigerant is decreased from thehigh pressure level HD to a low pressure level ND at a main expansionvalve 18. A shutoff valve 32 is in an open position, permitting therefrigerant at the low pressure level ND to flow through the evaporator34 and then through a low pressure side part of an interior heatexchange 30. From the internal heat exchanger 30 the refrigerant flowsto the compressor 12 to be compressed to the high pressure level HD.Because of a configuration of the metering device 22, no change in thepressure level of the refrigerant results from flowing through themetering device 22 during the cooling operation.

Conversely, during the heat pump operation shown in FIG. 1A, therefrigerant flows from the compressor 12 through the valve 14, through aheat register 16 to the main expansion valve 18. The refrigerant is atthe high pressure level HD up to the main expansion valve 18. At themain expansion valve 18, the pressure level of the refrigerant isdecreased to a medium pressure level MD. The refrigerant then flows fromthe main expansion valve 18 through the high pressure side of theinternal heat exchanger 20. Thereafter, the refrigerant flows throughthe refrigerant storage area 24 to the metering device 22. The meteringdevice 22 decreases a pressure level of the refrigerant from the mediumpressure level MD to the low pressure level ND in the flow direction ofthe heat pump. At the low pressure level ND, the refrigerant flowsthrough the condenser/gas cooler 26 operating as an evaporator. Ashutoff valve 28 is in an open position, permitting the refrigerant atthe low pressure level ND to flow to the low pressure side of theinternal heat exchanger 30. The refrigerant flows through the lowpressure side of the internal heat exchanger 30 and into the compressor12. At the compressor 12, the refrigerant is once again compressed tothe high pressure level HD.

According to the invention, during the heat pump operation, therefrigerant that flows through the high pressure side of the internalheat exchanger 20 is at the medium level pressure level MD, producing apotential heat exchange with the low pressure part of the internal heatexchanger 20. An advantage of the invention is that the refrigerantflowing through the low pressure part of the internal heat exchanger 30is heated or superheated before entry into the compressor 12. A suctionof a fluid refrigerant into the compressor 12 is militated against bythe superheating of the refrigerant. Accordingly, effective operation ofthe compressor 12 is maintained.

FIG. 2 shows the refrigerant circuit 10 of a vehicle air conditioneraccording to another embodiment of the invention. During the heat pumpoperation, the medium pressure level MD of the refrigerant is assured bya metering device 36. As a non-limiting example, the metering device 36is a conduit located between the main expansion valve 18 and the gascooler 26. An adjustment of a cross-section of the conduit 36 controls apressure of the refrigerant. The cross section of the conduit 36 isshown only schematically in FIG. 2. The cross section of the conduit 36is configured in such a manner to produce a loss of pressure during theheat pump operation, but not during the cooling operation. This can beachieved on the basis of the different conditions of the refrigerantduring the heat pump operation and the cooling operation. To ensure theaffect, a technical conduit analysis can be conducted separately foreach vehicle, in particular, as a function of conduit guidance orexisting bends.

In another advantageous embodiment shown in FIG. 3, the refrigerantcircuit 10 includes, in addition to the condenser/gas cooler 26, atleast one chiller 38 for heat exchange with the refrigerant circuit 10,such as that of a vehicle motor. Additional heat sources might also berepresented by an exhaust system or by various refrigerant circuits of apartially or fully electric vehicle.

In addition to the main expansion valve 18, metering devices 40, 42 arecontemplated to guarantee the medium pressure level MD in the highpressure part of the internal heat exchanger 20. Hence, the flow of therefrigerant can be guided either through the glycol heatexchanger/chiller 38, the condenser/gas cooler 26, or a combinationthereof. As a non-limiting example, the metering devices 40, 42 areadditional controllable expansion devices 40, 42. In a pass-throughposition of the metering devices 40, 42, the medium pressure level MDduring the heat pump operation is decreased to the low pressure level NDin order to be able to accept energy in the glycol heatexchanger/chiller 38 and/or the gas cooler 26. In this manner, therefrigerant circuit shown in FIG. 3 is advantageous because therefrigerant flowing into the high pressure side of the internal heatexchanger 20 is at the medium pressure level MD and can be used forsuperheating the refrigerant on the suction side of the compressor 12.

In addition, the pressure level of the refrigerant in the refrigerantstorage area 24 can be so adjusted by the defined setting of thecontrollable main expansion valve 18 and of the other metering devices40, 42 that as a result the storage of the refrigerant is assured at adensity that guarantees both efficient heating and an effective andreliable operation of the compressor 12.

FIG. 4 shows an embodiment of the refrigerant circuit 10 that, in itsfunction, essentially corresponds to the refrigerant circuit 10 shown inFIG. 3. As a distinction over FIG. 3, a connection conduit is employedwhich connects a flow channel through the condenser/gas cooler 26 to aflow channel through the glycol heat exchanger/chiller 38 via a shutoffvalve 44 downstream of the condenser/gas cooler 26 and the glycol heatexchanger/chiller 38. Accordingly, the condenser/gas cooler 26 and theglycol heat exchanger/chiller 38 shown in FIG. 4 are connected andoperate in parallel, while the condenser/gas cooler 26 and the glycolheat exchanger/chiller 38 shown in FIG. 3 are connected and operate inseries.

From the foregoing description, one ordinarily skilled in the art caneasily ascertain the essential characteristics of this invention and,without departing from the spirit and scope thereof, make variouschanges and modifications to the invention to adapt it to various usagesand conditions.

LIST OF REFERENCE NUMERALS

-   10 Refrigerant circuit-   12 Compressor-   14 Three-two way valve-   16 Heat register-   18 Controllable main expansion device-   20 Internal heat exchanger (high pressure)-   22 Damper-   24 Refrigerant storage area-   26 Condenser/gas cooler-   28 Shutoff valve-   30 Internal heat exchanger (low pressure)-   32 Shutoff valve-   34 Evaporator-   36 Conduit cross-section-   38 Glycol heat exchanger/chiller-   40 Controllable main expansion device-   42 Controllable main expansion device-   44 Shutoff valve-   ND Low pressure level-   MD Medium pressure level-   HD High pressure level

1. A refrigerant circuit for a vehicle, comprising: a compressorconfigured to compress a refrigerant; an internal heat exchanger influid communication with the compressor to receive the refrigeranttherein, the internal heat exchanger including a high pressure side partand a low pressure side part, wherein the high pressure side part is influid communication with at least one additional heat exchanger; and atleast one metering device configured to control a pressure level of therefrigerant, the at least one metering device in fluid communicationwith the internal heat exchanger, wherein the at least one meteringdevice permits the high pressure side part of the internal heatexchanger to receive the refrigerant during a heat pump operation of therefrigerant circuit between a pressure level at which the refrigerantexits the compressor and a pressure level at which the refrigerantenters the compressor.
 2. The refrigerant circuit of claim 1, whereinthe high pressure side part of the internal heat exchanger is in fluidcommunication with an expansion device.
 3. The refrigerant circuit ofclaim 1, wherein the at least one metering device is configured todecrease the pressure level of the refrigerant during the heat pumpoperation of the refrigerant circuit and maintain the pressure level ofthe refrigerant during a cooling operation thereof.
 4. The refrigerantcircuit of claim 1, wherein the at least one metering device is at leastone of a damper, a conduit, and a controllable expansion device.
 5. Therefrigerant circuit of claim 4, wherein the conduit has a cross-sectionwhich facilitates a decrease in the pressure level of the refrigerantduring the heat pump operation of the refrigerant circuit and maintainsthe pressure level of the refrigerant during a cooling operationthereof.
 6. The refrigerant circuit of claim 1, wherein the highpressure side part of the internal heat exchanger during the heat pumpoperation of the refrigerant circuit is upstream of the at least onemetering device.
 7. The refrigerant circuit of claim 1, wherein the atleast one additional heat exchanger is at least one of a condenser/gascooler and a glycol heat exchanger/chiller.
 8. The refrigerant circuitof claim 1, further comprising a refrigerant storage area disposedbetween the internal heat exchanger and the at least one additional heatexchanger.
 9. The refrigerant circuit of claim 8, wherein therefrigerant storage area during the heat pump operation of therefrigerant circuit is downstream of the high pressure side part of theinternal heat exchanger.
 10. The refrigerant circuit of claim 1, whereinthe at least one additional heat exchanger is operable with at least oneof water, air, exhaust gas, electronics, heat storage, solar heat, andsolar energy.
 11. A refrigerant circuit for a vehicle, comprising: acompressor configured to compress a refrigerant; an internal heatexchanger in fluid communication with the compressor to receive therefrigerant therein, the internal heat exchanger including a highpressure side part and a low pressure side part, wherein the highpressure side part is in fluid communication with a condenser/gas coolerand a heat exchanger/chiller; and at least one controllable expansiondevice configured to control a pressure level of the refrigerant, the atleast one controllable expansion device in fluid communication with theinternal heat exchanger, wherein the at least one controllable expansiondevice permits the high pressure side part of the internal heatexchanger to receive the refrigerant during a heat pump operation of therefrigerant circuit between a pressure level at which the refrigerantexits the compressor and a pressure level at which the refrigerantenters the compressor.
 12. The refrigerant circuit of claim 11, whereinthe high pressure side part of the internal heat exchanger is in fluidcommunication with an additional expansion device.
 13. The refrigerantcircuit of claim 11, wherein the at least one controllable expansiondevice is configured to decrease the pressure level of the refrigerantduring the heat pump operation of the refrigerant circuit and maintainthe pressure level of the refrigerant during a cooling operationthereof.
 14. The refrigerant circuit of claim 11, wherein the highpressure side part of the internal heat exchanger during the heat pumpoperation of the refrigerant circuit is upstream of the at least onecontrollable expansion device.
 15. The refrigerant circuit of claim 11,wherein the at least one controllable expansion device is disposedbetween the internal heat exchanger and at least one of thecondenser/gas cooler and the heat exchanger/chiller.
 16. The refrigerantcircuit of claim 11, further comprising a refrigerant storage areadisposed between the internal heat exchanger and at least one of thecondenser/gas cooler and the heat exchanger/chiller.
 17. The refrigerantcircuit of claim 11, wherein the condenser/gas cooler and the heatexchanger/chiller are connected in one of parallel and series.
 18. Therefrigerant circuit of claim 11, wherein the heat exchanger/chiller isin heat exchange relationship with a motor refrigerant circuit.
 19. Arefrigerant circuit for a vehicle, comprising: a compressor configuredto compress a refrigerant; an internal heat exchanger in fluidcommunication with the compressor to receive the refrigerant therein,the internal heat exchanger including a high pressure side part and alow pressure side part, wherein the high pressure side part is in fluidcommunication with a condenser/gas cooler and a heat exchanger/chiller;a first controllable expansion device configured to decrease a pressurelevel of the refrigerant, the first controllable expansion device influid communication with the internal heat exchanger and thecondenser/gas cooler, wherein the first controllable expansion devicepermits the high pressure side part of the internal heat exchanger toreceive the refrigerant during a heat pump operation of the refrigerantcircuit between a pressure level at which the refrigerant exits thecompressor and a pressure level at which the refrigerant enters thecompressor; and a second controllable expansion device configured todecrease a pressure level of the refrigerant, the second controllableexpansion device in fluid communication with the internal heat exchangerand the heat exchanger/chiller, wherein the second controllableexpansion device permits the high pressure side part of the internalheat exchanger to receive the refrigerant during the heat pump operationof the refrigerant circuit between the pressure level at which therefrigerant exits the compressor and the pressure level at which therefrigerant enters the compressor.
 20. The refrigerant circuit of claim19, wherein the second controllable expansion device and the firstcontrollable expansion device can be operated at least one ofindividually, alternatingly, synchronously, and any combination thereof.